As wireless electronic products are manufactured with a short, small, light and thin design, the space within a casing of the wireless electronic product is decreased greatly, and the area reserved on a printed circuit board of the wireless electronic product for installing an antenna becomes very small, and thus research and development engineers and manufacturers attempt to print antennas in different shapes (such as a circular or polygonal shape) on the printed circuit board, and try to find an antenna with the most appropriate shape and size and having a lower cost and an easy-to-adjust feature. However, no antenna with the aforementioned conditions has been designed on a printed circuit board yet, mainly because the production conditions such as the mass production and the high production yield rate have to be taken into consideration for the actual production of the antennas.
Based on the foregoing reasons, designers and manufacturers designed and developed a microstrip bell-shaped antenna as shown in FIG. 1, wherein electronic components and circuits of a wireless electronic product are installed on a printed circuit board 1 of the wireless electronic product, and the printed circuit board 1 has a bell-shaped antenna 10 printed at a position adjacent to an end of the printed circuit board 1, and both sides of the bell-shaped antenna 10 are expanded towards both sides of the printed circuit board 1, and a microstrip feedline 12 is extended to a position adjacent to an another end of the printed circuit board 1, and an end of the microstrip feedline 12 is connected to a signal line (not shown in the figure) of the printed circuit board 1, such that the outwardly extended shape of the bell-shaped antenna 10 allows the current produced by the microstrip feedline 12 due to an electro-inductive effect to flow along a tapered path on both sides of the bell-shaped antenna 10, and the current can be distributed uniformly on the bell-shaped antenna 10 to effectively reduce the electro-inductive effect of the microstrip feedline 12 and provide the required bandwidth. Since the bell-shaped antenna 10 can be printed directly onto the printed circuit board 1, the bell-shaped antenna 10 can meet the requirements for mass productions and a high yield of the production.
For example, the maximum width of the bell-shaped antenna as shown in FIG. 1 is equal to 17.87 mm; the maximum length is equal to 15.558 mm; and the bandwidth falls within a range of 1.912059 GHz˜4.967982 GHz (as shown in FIG. 2) to cover the frequency required by a ultra wideband (UWB) wireless electronic product. However, some wireless electronic products designed according to customer requirements have narrow space in their casing, such that after the positions of electronic components and circuits on the printed circuit board are adjusted, the area reserved on the printed circuit board for printing the bell-shaped antenna is insufficient. Therefore, finding a way of manufacturing an antenna with a bandwidth and electric properties similar to those of the bell-shaped antenna demands immediate attentions and feasible solutions.